How Does Zero Gravity Effect the body?

After more than 50 years of human spaceflight, NASA is an expert in what happens to the human body when it’s in zero gravity.

This research has ensured that astronauts could safely walk on the moon and live for more than a year on the International Space Station, 220 miles above the Earth’s surface. But the Human Research Program, which aims to lessen the effects of the space environment on the health and performance of humans, is using the data to make sure they can send astronauts even deeper into the solar system.

A six-month journey to Mars would only be the beginning of a challenging expedition to land people on the surface of the Red Planet, 140 million miles away. The crew members would then live and work there.

In preparation, NASA has been using six-month crew member rotations and Scott Kelly’s groundbreaking one-year mission on the ISS to study the effects of space on the human body. So what happens when we have to transition from walking on solid ground to floating in zero gravity?

Mike Hopkins during a 2013 spacewalk.

“I felt like I was falling,” NASA astronaut Mike Hopkins told CNN’s Rachel Crane. “It was as if you’re hanging off the rafters in a building and you let go, and that lasted for about 24 hours. My brain was taking a little while to get used to the fact that there was no up and down anymore. And that went away fairly quick. It takes a little while to get used to floating, too. It’s almost like learning to walk all over again, a little bit.”

Hopkins was on the ISS for 166 days, from September 2013 to March 2014. Though the adjustment to microgravity doesn’t take long, other issues arise within the first few days due to a phenomenon in which the head tilts downward between 12 and 20 degrees, which causes disorientation.

“As soon as you arrive in weightlessness, the fluids start shifting in your body from the lower part of your body into the upper part of your body,” said Dr. John Charles, Human Research Program associate manager for international science. “Your organs of balance and your inner ear immediately sense there’s no gravity pulling down on them anymore.”

This causes something known among astronauts as Bird Leg Syndrome, because the fluid shift causes them to have puffy faces and thin legs. It also makes them less thirsty, dulls their sense of taste and causes a “stuffy nose” feeling similar to allergies. Space motion sickness also affects about 79% of astronauts who experience microgravity in the first 24 to 48 hours, creating a loss of appetite, dizziness and vomiting.

Long-term risks

Hopkins also had to worry about the long-term effects on his body, such as the weakening and loss of bones and atrophying muscles. In space, without gravity, bones lose more than 1% of minerals and density per month.

Astronauts also experience blood volume loss, weakened immune systems and cardiovascular deconditioning since floating takes little effort and the heart doesn’t have to work as hard to pump blood through your body, according to Human Research Program deputy chief scientist Jennifer A. Fogarty.